Field of the Invention
The invention disclosed herein relates to exploration for oil and gas and, in particular, to a downhole instrument for production well-logging.
Description of the Related Art
In the exploration for oil and gas, it is necessary to drill a wellbore into the Earth. Evaluation of the Earth and the surrounding formations is often undertaken with the use of sophisticated tooling lowered into the wellbore. Evaluations, or well-logging, may be completed while drilling (measurement while drilling, (MWD or LWD)) or after drilling, such as by lowering of a wireline.
A variety of instruments may be used. Instruments that are directed to technologies such as radiation measurement (gamma and neutron generation), and measurements involving acoustic, seismic, resistivity, magnetic resonance, are often used as is fluid sampling, and various other forms of spectroscopy. Unfortunately, the various tools and instruments that are useful for well logging generally involve intricate equipment that requires a connection to a power supply and other ancillary equipment topside. Therefore, logging equipment is removed from the well before a well enters into production.
However, removing logging equipment from a well leaves operators in a situation where it is impossible to characterize the resources downhole. Accordingly, operators periodically stop production to conduct well logging and assess a health of a respective production well. Of course, cessation of production has a great financial impact on the operator.
Thus, what are needed are methods and apparatus suited for conducting well logging in a production environment. Preferably, the methods and apparatus should provide for a variety of types of analyses with minimal impact on production.